Chapter 15 Flashcards
What is included in the somatosensory system?
The cutaneous senses
Proprioception
Kinesthesis
What is the function of skin?
Warning functions
Protects us from bacteria, chemical agents, and dirt from penetrating or bodies
Provides us with information about the stimuli we come into contact with
What is the epidermis?
The outer layer of skin
What is the dermis?
A layer of skin below the epidermis
What are mechanoreceptors?
Receptors that respond to mechanical stimulation
What is a Merkel receptor?
Mechanoreceptor
Located close to the surface of the skin, small receptive field
Slowly adapting fiber, fire as long as the stimulus is on
What is a Meissner corpuscle?
Mechanoreceptor
Located close to the surface of the skin, small receptive field
Rapidly adapting fiber, fires only when the stimulus is applied and removed
What is a Ruffini cylinder?
Slowly adapting fiber that responds continuously to stimuli
Located deep in the skin, large receptive field
Senses stretching of the skin
What is a Pacinian corpuscle?
Rapidly adapting fiber that responds when the stimulus is applied or removed
Located deep in the skin, large receptive field
Responds to rapid vibration and fine texture
What is the medial lemniscal pathway?
Has large fibers that carry signals related to proprioception and perceiving tough
Transmits the signals at a high speed
What is the spinothalamic pathway?
Consists of smaller fibers that transmit signals related to temperature and pain
How does touch reach the cortex?
Signals enter the spinal cord through the dorsal root, either goes through the medial lemniscal or spinothalamic pathways, and then fibers from both pathways cross over to the other side of the body and synapse in the thalamus and then go to the somatosensory cortex
What are the two areas that receive signals from the thalamus?
The primary somatosensory cortex in the parietal lobe
The secondary somatosensory cortex
What is the insula?
Important for sensing light touch
What is the anterior cingulate cortex?
Involed in pain
What is tactile acuity?
The capacity to detect details of stimuli presented to the skin
How do we measure tactile acuity?
Using the two-point threshold
Grating acuity
What is the two-point threshold?
The minimum separation between two points on the skin that when stimulated is perceived as two points
What spacing of Merkel receptors corresponds with a greater tactile acuity?
When they are spaced closer together
What is evidence that Pacinian corpuscles respond to vibration?
They respond very poorly to slow or constant pushing but well to high rates of vibration
What is surface texture?
The physical texture of a surface created by peaks and valleys
What is the duplex theory of texture perception?
Our perception of texture depends on both spatial cues and temporal cues
What are spatial cues in somatosensation?
They are provided by relatively large surface elements that can be felt both when the skin moves across the surface elements and when it is pressed onto the elements
What are temporal cues in somatosensation?
They occur when the skin moves across a textured surface like fine sandpaper
Responsible for our perception of fine texture that cannot be detected unless the fingers are moving across the surface
What did the patterns of monkeys having texture scanned across their fingertips show?
Different textures cause different firing patterns in an individual neuron
Different neurons responded differently to the same texture
Which neurons respond best to coarse textures?
SA1 neurons, Merkel receptors
What neurons respond best to fine textures?
Pacinian corpuscles
What is active touch?
Touch in which a person actively explores an object
What is passive touch?
Occurs when touch stimuli are applied to the skin
What is haptic perception?
Perception in which 3D objects are explored with the fingers and hand
What is social touch?
When one person touches another person
What are CT afferents?
Unmyelinated nerve fibers that is involved in social touch on hairy skin
What is microneurography?
Inserting a metal electrode with a very fine tip just under the skin
What is the social touch hypothesis?
CT afferents and their central projections are responsible for social touch
What are the discriminative functions of touch?
Sensing details, texture, vibration, and objects
What is the affective function of touch?
Sensing pleasure and therefore eliciting positive emotions
What is inflammatory pain?
Caused by damage to tissue or inflammation of joints or by tumor cells
What is neuropathic pain?
Caused by lesions or other damage to the nervous system
What is nociceptive pain?
Caused by the activation of receptors in the skin called nociceptors that are specialized to respond to tissue damage or potential damage
What is the direct pathway model of pain?
Pain occurs when nociceptor receptors in the skin are stimulated and send their signals directly from the skin to the brain
What are phantom limbs?
Pain that occurs without any transmission from receptor to brain as amputees experience discomfort where their missing limbs was
What is the gate control model of pain?
The idea that pain signals enter the spinal cord from the body and are then transmitted from the spinal cord to the brain
Proposes additional pathways that influence the signals sent from the spinal cord to the brain
Signals from these additional pathways act as a gate
What can pain be influenced by?
Expectations, attention, emotions
What is the placebo effect?
A decrease in pain from a substance that has no pharmacological effects
Believing that a medication will work will cause a reduction in pain
How can attention affect pain?
We might not experience pain until we realize that we are injured
What types of emotions are related to less pain experience?
Positive emotions
Which structures become activated by pain?
Hypothalamus
Amygdala
Thalamus
S1
Anterior cingulate cortex
Prefrontal cortex
Insula
What transmitter acts on opioid receptors?
Endorphins (natural morphine)
What will decrease the analgesic effect of endorphins?
Naloxone
Suggests that pain reduction due to placebos occurs because of the release of endorphins
How does social touch reduce pain?
Holding hands causes synchronized brain waves which are translated into reduced pain
Holding hands reduces activity in brain areas associated with pain
What parts of the brain are activated when observing someone else in pain?
The anterior cingulate cortex and the anterior insula which are involved in the affective component of pain
What is social pain?
Paine caused by social interactions
What is activated by feelings of social exclusion?
The dorsal anterior cingulate cortex
What is the physical-social-pain overlap hypothesis?
Proposes that pain resulting from negative social experiences is processed by some of the same neural circuitry that processes physical pain
What did neural mind-reading find about social pain?
The pattern of voxel response for social rejection is different than that of painful heat stimuli applied to the forearm
Different neurons/circuits within the same area?
What is hand dystonia?
A condition that causes the fingers on one hand curl into the palm
